https://metadata.nostr.com/ is the only client that allows you to define petnames for your contacts: 
Hopefully someday this will still be big and we can have our petname based DNS and stuff like that, and not need NIP-05 for human-readable names.
Discussion
Great, Jaf Nissan 🤝
Here's a nice read about petname systems: https://spritelyproject.org/news/petname-systems.html
I like this. Very simple.
In my humble opinion Nostr has the possibility to get a much bigger audience if it had built in support for nicknames… Twitter users could connect with all their usual buds who share their ideologies, easier to switch platforms… Twitter is still a really good place for me to find breaking news stories, along with the unavoidable nonsensical dumpster fires that rage out of control there…
Nicknames like Twitter? The problem is that doesn't work on decentralized systems. See Zooko's triangle.
We all have our names tied to the “npubs” + there’s this directory that helps you find folks you follow on Twitter https://nostr.directory
Yeah, I get it, have seen the directory… but that’s still a separate place to go for the directory… and I get the slow and steady Nostr growth… understand that viewpoint… for now not easy for the non technical users… but it is what is… and yes, Twitter is still there for late breaking news told from one’s own news bubble/cocoon of choice… party on, Garth!!
I don’t think it has to be either/or. (Unless you get banned or suspended from Twitter lol.) Nostr offers a different user experience which is worth trying out. Rapid growth isn’t necessary. Slow and steady ultimately wins.
I think it would be good to store pet and edgenames in an encrypted way, so that users don’t leak each others real names.
I see what you mean, but the point of petnames, for me, is to allow others to see how you refer to each contact, so it must be public by necessity. I do think we need apps that keep private contact lists, stored locally or saved as encrypted blobs under NIP-78 though.
I don't know. I am quite concerned my 'normal user' friends would leak my realname eventually.